is a key character in the various Tenchi Muyo!anime series by AIC. While details of her character differ between the various series, Ryoko is typically shown as an attractive, semi-reformed powerful space pirate who is madly in love with the series main character, Tenchi Masaki. In the various series, Ryoko is portrayed as being impulsive, hedonistic (with a penchant for sake), poor-mannered, often immodest, recklessly violent, and hot-tempered although she sometimes reveals her more emotional and vulnerable side. .

In the anime, Ryoko universally holds an intense rivalry with the character Ayeka, who also fights for Tenchi's affections. Often the conflict between the two comes out of their decidedly different personalities, with Ryoko being the tomboyish troublemaker and Ayeka being the well-mannered, but often snooty aristocrat. The level of the rivalry can vary between being equitable to a pair of bickering siblings to an all-out feud.

While the name Ryoko is a common feminine given name in Japan, in this instance it is written with very uncommon kanji. Ryoko's name can be translated as "bringer of demons" and is stated as meaning "The Devil Caller" in the OVA series.

She was created by Washu, using one of her egg cells as a base, so she is indirectly (raised in a tube with no contact with Washu) Washu's daughter. Washu's DNA was combined with that of amorphous creatures called the Masu to create Ryoko. She has three red gems that are the source of her full energy, which also came from Washu when she imbued them with her godly powers in her early life.